A novel photocatalytic system coupling metal-free Carbon/g-C3N4 catalyst with persulfate for highly efficient degradation of organic pollutants

A variety of photocatalytic systems have emerged as the effective methods for the degradation of organic pollutants. In this research, a novel photocatalytic system, named CNC-PDS has been proposed, which couples a metal-free carbon/g-C3N4 (CNC) photocatalyst with persulfate (PDS), and applied for efficient degradation of paracetamol (PCM) under simulated sunlight. The CNC-PDS system exhibited excellent photocatalytic capability, where the PCM was completely degraded in 40 min under simulated sunlight. The degradation rate of CNC-PDS system was 9.5 times compared with the g-C3N4 and PDS coupled systems. The CNC-PDS system can efficiently degrade other representative pollutants in neutral solutions, such as pharmaceuticals, endocrine disrupting compounds (EDCs), azo dyes. The excellent catalytic activity of CNC-PDS system should be ascribed to the two aspects: a) the increased light absorption range led to more photo-induced electron-hole pairs generation compared with the original g-C3N4. Meanwhile, the charge separation efficiency of the CNC photocatalyst was drastically enhanced which was proved by the results of PL and EIS analysis. These results represented the carbon/g-C3N4 might offer more e- to promote PDS activation. b) The introduction of CO and the improved specific surface area provided more active sites for PDS activation. In addition, the EPR analysis and quenching experiments indicated that O2.-, h+ and 1O2 were the main active species for PCM in the CNC-PDS system under simulated sunlight, and the contribution order was O2.->1O2>h+. The degradation pathways of PCM in the CNC-PDS system are proposed based on the results of HPLC-MS. The novel CNC-PDS photocatalytic system has provided a viable option for treatment of contaminated water by organic pollutants.